The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jan. 25, 2005
Filed:
May. 23, 2003
Christopher Francis Edwards, Sunnyvale, CA (US);
Craig Alexander Easson, Sunnyvale, CA (US);
Madhavprasad V. Kolluri, Sunnyvale, CA (US);
Anthony Stephen Doy, Sunnyvale, CA (US);
Christopher Francis Edwards, Sunnyvale, CA (US);
Craig Alexander Easson, Sunnyvale, CA (US);
Madhavprasad V. Kolluri, Sunnyvale, CA (US);
Anthony Stephen Doy, Sunnyvale, CA (US);
Maxim Integrated Products, Inc., Sunnyvale, CA (US);
Abstract
Method and apparatus to enable the use of class D amplifiers without the need for an output filter, while maintaining both a high efficiency and a high audio fidelity. Using the classic differential Pulse Width Modulation scheme, the high frequency carrier is first suppressed to achieve a ternary modulation, and then re-introduced as a common mode pulse whose width is modulated to provide the necessary output voltage, but whose width never decreases below a well-defined threshold. The frequency of the modulator waveform (ramp or triangle) may itself be modulated on a sample-by-sample basis, so that the EMI spectrum of the output waveforms can be made white at high frequencies. The combination of the modulation scheme and spread spectrum high frequency behavior allows the user to eliminate the external filter. Various embodiments are disclosed.